Inline Mains booster pumps (combi system)

[hotspot007]

Has anyone any experience with inline booster pumps.
I'm looking at the salamander home boost and the Stuart Turner flomate.
Do they work OK, are they worth it?
I want to increase the pressure & flow in my shower from 9litres a min to 12litres n min. Current static pressure of 2bar, dynamic of 1.4bar.
Many thanks

 

[oldbutnotdead]

Your combi is probably the hard limit in your system- there is a finite volume of water the thing can get up to showering temperature from cold per minute. Have a look in your boiler specifications- it'll tell you something like x LTRs/min at Δ35 °C . Remember that's under test conditions, burner probably tuned for best performance flat out so whatever number you get, derate by 10% for real world.

 

[hotspot007]

I have a greenstar 30si.... Think max flow is 12litres a min

 

[oldbutnotdead]

14.3l/min at Δ30, 10.8 at Δ40 ± 15% - that sounds very suspicious (the plus/minus bit).
How hot do you like your showers?- try adjusting the dhw temp, see what happens

 

[hotspot007]

Set the temp on the boiler to max temp now. Removed the thermostatic shower bar and put on a manual mixer - so hot water is fully open and adjust the cold to suit.
Pressure/flow no different.
Been having issues with showers going hot and cold - Bgas came and looked and blamed the mains pressure. I'm thinking more the hex is blocked restricting the flow down to 6litres a min hot.

 

[oldbutnotdead]

How's the dhw flow at the kitchen hot tap (or whatever is nearest the boiler). How well does shower hot run if you remove the shower head? And if you remove the shower hose? Has this been a forever problem, how much of the history of the system do you have (clumsy way of saying have you lived there for years and years or only a few months)?

 

[hotspot007]

The flow is the same at the kitchen hot tap as the shower outlet... Same flow with hose and shower head removed.
Lived here since built 8 years ago, so no additions to any of the system, and issue started maybe 6 months ago.

 

[oldbutnotdead]

Fair enough. Any new build estates round your way? How's the cold water flow rate (kitchen tap or outside tap if you have one & its first off the main)

 

[hotspot007]

Oddly.. Kitchen tap is around 9/10 litres min, but my cold bath is 15 litres a min dnt get that.

 

[oldbutnotdead]

Interesting. How old is the house (ish)- are there any tanks in the loft? Is any pipework visible anywhere. How's the hot flow at the bath?

 

[Madrab]

Is your kitchen tap a mixer? If so then it's probably through narrow flexi hoses and a water saving aerator nozzle and with a dynamic pressure of 1.4bar then flow will be reduced. If so then don't test your mains at the kitchen tap, test at an outside tap or similar full flow tap.

As suggested, is the bath from the mains too and are they separate H/C taps?

 

[hotspot007]

The house is 8 years old, I've been here since new. It's just a small housing site of 16 new houses.
The loft - top floor is a bedroom and ensuite with shower and basin. The kitchen tap is a mixer but with 2 separate taps - that's piped underneath straight off 15mm copper. The bathroom has been piped in white plastic using hep2o 15mm.
The garden tap is just T'd off the same 15mm copper pipe that feeds the kitchen tap and boiler. So at kitchen tap = 9/10 litres min, outside tap just open ended ie no hose = the same 9/10 litres a min. The cold in the bath = around 15 litres a min.
The hot flow is 6 litres a min everywhere I measure. Kitchen tap, bath, ensuite basin, ensuite shower.
The flow at the shower when mixed is 8/9 litres a min.
There's no water tank anywhere. (been behind ensuite in loft space as I use for storage. There was a TMV under the bath which T'd off the hit and cold and fed all 3 basins - ground floor basin, bathroom basin and ensuite basin. This was passing - so I've just this week removed it! Due to part of the tshooting for said issues I've been having. But the TMV was just a red herring anyway as it definitely did not feed my shower. It's just fed the 3 basins.
I have the original documents from when I moved in. The boiler was commissioned at static pressure of 2bar and the differential temp measured at 9litres a min at kitchen tap.
I still have the 2 bar - just now the flow is down to 6 L /min.
I've had bgas out - they blamed low mains pressure - changed the flow restrictor and housing and left.(nothing changed with the change of the flow restrictor). That's what sent me on the journey of finding out all my information (that I didn't have at the time of his visit ie commissioning data, static and dynamic pressures, and led me on the journey of finding all my basin mixer taps passing - as in with the hot isolated at the boiler, water was still coming out the hot).
So I'm back where I started with the hot/cold shower issue - that I think it's boiler related, and the hex is furred up reducing the flow from 9 (original) to now 6

 

[oldbutnotdead]

Ta for info- I was wondering whether the combi was a retrofit on an old vented system. The high speed bath tap is very intriguing. Have you found where cold gets into the house yet?
Given you have that decent flow at the bath tap (and given you're obviously comfy with playing with pipework) it would be very tempting to invest £30 in a spool of 15mm placcie (or go 22 to make sure) and do a temporary swap on the cold feed to the combi (pushfits do have a place in the universe and this is it)- see if improving the supply improves the output before doing £100s on boost pumps.
Highly possible the pipework is a rat's nest with no thought about efficient operation, just chuck it in quick. It's also possible that boiler innards are furred up (does your kettle scale up?)

 

[hotspot007]

Thanks for the reply.
Yeah... Oddly my water comes in, in my lounge - I have a cupboard in there where the blue Mdpe comes up out the floor - into my water meter - then 15mm copper out into the wall. I assume this then goes up and services the main bathroom first - then down into the kitchen., and up to the ensuite. As I've said previous - the bath taps are piped in 15mm plastic pipes with hep2o quick connectors. However they come up out the floor - so don't know where it goes from copper to plastic. The issue I have also is the flooring... Dreaded tongue and groove boarding.
What difference would feeding the boiler in plastic rather than copper make?

 

[hotspot007]

Ahh get you. You mean just run a length in plastic to see if the flow through the boiler improves.
Is it possible (given regs and everything) - on new houses they fit some kind of flow restrictor - say the cold feed to the bath is from the mains (after water meter) then the rest of the house is fed from this with some kind of restriction.?